Blooms of the dinoflagelate ostreopsis and human respiratory disorders in the Mediterranean: Where are we?

Abstract

Since the last decades, blooms of the toxic dinoflagellate Ostreopsis in temperate areas have increased. In some Mediterranean localities, massive outbreaks have been related to respiratory and dermatological symptoms, although the direct link between the two events is not clearly established yet. To increase the understanding of the bloom dynamics, diverse studies have been conducted in Sant Andreu de Llavaneres (NW Mediterranean), an Ostreopsis blooms hot spot. In the 2009-2010 outbreaks (EBITOX project), Palytoxin-like compounds (PLTX, 0.1 - 1.2 pg/cell) were detected in the microepiphytic assemblages dominated by Ostreopsis, but the concentrations in the aerosol (obtained by high-volume air pump samplers) were below the detection limit. Surprisingly, some marine microalgae were observed (by Scanning Electron Microscopy) in the aerosol filters, and up to 100 cells of Ostreopsis cf. ovata per filter were estimated by qPCR assay. Furthermore, high bacterial abundances and activity coincided with Ostreopsis blooms, although the link of some strains (e.g. Vibrio) with the bloom toxicity may be precluded. Finally, the joint epidemiology and ecology study conducted last summer-autumn, revealed that human health disorders peak coincided with the transition from the exponential to the stationary phase of the O. cf. ovata bloom. PLTX, other secondary metabolites and/or potentially allergenic substances from the associated microbial community, could be released to the environment coinciding with that particular physiological state of the Ostreopsis cells and/or the accompanying microplankton community. Thereafter, despite high cell densities in the macroalgae respiratory impacts were not detected